Thin wire annealing using discharge plasma in atmospheric pressure

In this study, as one of possible applications of dielectric barrier discharge plasma in atmospheric pressure, annealing a metal thin wire is researched. The discharge plasma can heat the copper wire, and remove extraneous matters. The main purpose is to examine the annealing effect by using atmospheric pressure plasma, and investigate the surface cleaning effect for metal wire. The thin metal wire is mainly in use electronics devices. The wire manufacture currently consists of three processes, stretching, annealing, and cleaning. The annealing can remove the residual stress for the wire after the stretching process, and improve the ductility. We propose that the annealing and cleaning processes can be simultaneously operated by using discharge plasma with a reactor in atmospheric pressure. Furthermore we study the power supply system, from the view points of cost, simplicity, and maintenance ability. The experimental setup is composed of a gas tank, a plasma reactor, and a power supply. Helium or argon gas is filed into the reactor from the gas tank. The reactor shapes are the plane and the coaxial cylindrical geometries. The inverter with the voltage (10 kV) at frequency range of 35-45 kHz is used for both the reactors. Also the power supply (20 kV, 50 Hz) by a high-voltage transformer is used. The diameter of a metal wire is 0.2 mm, and the requirement of the elongation rate is set as over 20 %. The elongation rate is measured by SAIKAWA ET-100. The experimental results indicate the plasma annealing method has an increase effect for the elongation rate. Furthermore it is confirmed that by using a scanning electron microscope (SEM). As a result, the copper wire surface was cleaned by the atmospheric plasma. We also confirmed the thermal input from the surface of the wire heat the center of the copper wire in the plasma annealing using by a numerical simulation.